This invention relates to a process and apparatus for the recovery of energy from a gas/liquid mixture, primarily a gas and oil/water mixture from an oil well.
The general concept of recovering energy from a well stream, whether it be a hydrocarbon well, or a geothermal well, is known. For example, U.S. Pat. No. 5,385,446 shows the use of a rotary separation turbine to recover energy, from, and separate the constituents of a gas liquid mixture from a geothermal well. U.S. Pat. No. 5,117,908 shows that it is known to use a rotary turbine to recover energy from the gas/liquid mixture in the well stream of an oil well as a stage prior to the separation of the gas/liquid mixture.
Rotary separation turbines, for example of the kind illustrated in U.S. Pat. No. 5,385,446 incorporate a specifically designed nozzle through which the inlet mixture is directed into the rotary separation turbine. The present invention is based upon the recognition that such rotary separation turbines are designed to operate with optimum efficiency when supplied at a predetermined flow rate, with a mixture having a predetermined gas/liquid ratio.
In accordance with the present invention there is provided a process for the recovery of energy from a pressurised well stream containing a gas/liquid mixture, the process comprising treating the well stream to a pre-separation process to separate it into gaseous and liquid phases, selecting appropriate proportions of said separated gaseous and liquid phases, recombining said selected proportions, and supplying the recombined mixture to the inlet of a rotary separation turbine wherein said components are separated and energy is recovered from the flow by rotation of the turbine, said proportions of said gaseous and liquid phases being selected to produce an optimum mixture for supply to the rotary separation turbine.
The invention further resides in an apparatus for recovering energy from a well stream comprising a pre-separation device for separation of the well stream into gaseous and liquid components, selection means for selecting predetermined proportions of said gaseous and liquid components, mixing means for recombining said selected proportions, and a rotary separation turbine driven by said recombined mixture.